1. Field of Invention
This invention relates to a semiconductor memory device having a double stacked capacitor and a method for manufacturing the same, and more particularly to a semiconductor memory device having a double stacked capacitor the capacitance of which can be increased by forming a dielectric film on the wall of a contact hole of the capacitor when the contact hole is formed to electrically connect a plurality of electrodes to each other in the double stacked capacitor, and a method for manufacturing such memory device.
2. Information Disclosure Statement
So far, many kinds of dynamic random access memory (DRAM) devices had been developed, and as the integrity of the DRAM devices increases, such devices may be classified into a trench type device and a stacked type device depending upon the capacitor structure formed in the memory device.
In the case of the stacked type memory device, as the integrity of the memory devices increases, the area of unit cell of the memory device decreases. Thus, there is a limit to increasing the capacitance of capacitor in the memory device. In the prior art, attempts had been made to overcome such limitation. For example, one attempt formed a double stacked capacitor in which one plate electrode is positioned on the charge storage electrode and the other plate electrode is positioned under the charge storage electrode, that is, the charge storage electrode is sandwiched in between two plate electrodes.
Another attempt formed a different double stacked capacitor in which one charge storage electrodes is positioned on the plate electrode and the other charge storage electrode is positioned under the plate electrode, that is, the plate electrode is sandwiched in between charge storage electrodes.
In such approaches using the double stacked capacitor, when a contact grove is formed on a portion of the plate electrode on the drain region to connect the charge storage electrode and the drain region, or when a contact hole is formed on a portion of the plate electrode on the one charge storage electrode to connect *the one charge storage electrode and the other charge storage electrode, oxide film spacers are formed on the sidewall (the sidewall of the plate electrode) of contact hole, thereby protecting against a short circuit between the plate electrode and the charge storage electrode simultaneously with connecting electrodes.
However, since the oxide film spacers are formed on the sidewall of the contact hole, the oxide film spacers cannot function as the dielectrics of capacitor. Thus, the effective area of the capacitor is decreased as much as the area of the sidewall of the spacers.
Therefore, it is an object of the present invention to provide a semiconductor memory having a double stacked capacitor in which the effective area of the capacitor is increased by forming dielectric films instead of forming an insulating film spacers on the sidewall of a contact hole in the same double stacked capacitor as that of the prior art semiconductor memory device described above, and to provide a method for manufacturing such memory device.
According to the present invention, more capacitance which is proportional to the surface area of the dielectric formed on the contact hole can be obtained as compared to the prior art double stacked capacitor.